This invention relates to a solar-powered monitor and more particularly to a solar-powered monitor for checking the operability of the solar-module, for providing surveillance over a defined area and for other uses.
Monitors which maintain surveillance over banks, factories, offices and the like are well known. In some such devices, cameras are used to monitor a defined area while in others, sensors such as pressure switches, motion detectors, glass breakage detectors and the like activate an alarm. Such devices are activated by electrical energy derived from conventional sources such as hydro electric power, coal-fired generators and so on. Such energy is supplemented by batteries in the event of an interruption in power.
A shortcoming of conventional monitors is that they cannot be used in locations where conventional sources of energy are unavailable. Such power is not available in vast areas of the arctic, for example, and conventional monitors cannot be used there. In other areas, such power may be available but at such high cost that the benefit from a monitor may be overridden by the cost of supplying it wit such power.
I have invented a solar powered monitor which is suitable for use in remote locations where conventional sources of electrical power are not available or where the cost of supplying the monitor with such power is prohibitive. The monitor can be installed where it is most suited for use without regard to the availability of conventional power.
Power is derived from a bank of solar cells commonly referred to as a xe2x80x9csolar modulexe2x80x9d. The module may not generate power during daylight hours because it is defective or because it is deliberately or accidentally shielded from the sun. To detect is, the electrical output from the solar module is continuously or periodically monitored so that if the module fails to generate a predetermine electrical output, his information is relayed to a manned station where steps can be taken to remedy the situation.
A micro-controller is used to monitor the fluctuations in electrical output from the solar module over a given period of time. The controller does so by measuring the length of each interval or period of time during which the output falls below a given value. The length of that interval is added to the of previous like time intervals. The accumulated length of such time intervals is stored in memory and when it reaches a predetermined value or when a given period of time has elapsed, the micro-controller relays that information to the manned station.
By way of example, the micro-controller might be programmed to measure the accumulated lengths of time intervals that the output from the solar modulo was below 10 milliamperes. When the accumulated lengths of time intervals reached a predetermined value, for example 2 hours, the contoller would send a signal to the manner station. Alternatively, the micro-controller would be programmed, a the end of every 24 hours, to report a number to the manned station. The number might be 15.5 which would represent the accumulated total of all such intervals of time during that 24 hour period
It is important to note that the monitor of the invention is not intended to report each instance when the output from the solar module is below the given value. What it is intended to do is to accumulate the lengths of all such time intervals until those lengths reach a predetermine value. Alternatively the monitor accumulates the lengths of such time intervals over a predetermined period of time.
The time of year and climatic occurrences, such as heavy clouds, rain, snow must be taken into account to interpret the information generated by the micro-processor. If, for example, there was a heavy cloud cover for a period of 2 hours during daylight hours of the 24 hour period, the monitor would be expected to report a period of 2 hours plus the number of night-time hours during that 24 hour period. If the monitor reported a higher number than this, there could be a problem. The solar module, for example, could be defective or the module could be deliberately shielded from the sun.
The monitor of the invention is intended to report problems that occur over a relatively lengthy period. While that period is adjustable and can be shortened to the point where the monitor effectively reports problems as they occur, this is not the primary function of the monitor. The monitor is intended for use in remote location where measures to correct a problem cannot be taken immediately because, for example, there is no one in the vicinity of the monitor to do so. The monitor""s primary function is to record and transmit information that reflects a problem which may exist for a lengthy period of time and which will not, under normal circumstances, be corrected immediately.
A rechargeable battery is provided for storing energy from the solar module. That energy is available when the module fails to generate sufficient energy to activate the monitor such as at night. Thus the monitor continues to operate even tough the solar module may be defective or the module my be deliberately shielded from the sun.
A temperature sensor measures ambient temperature surrounding the battery and adjusts the voltage of the electrical output of the solar module according to changes in such temperature. Optimal conditions for charging the battery are accordingly maintained.
Briefly, the solar-powered monitor of the invention includes a photovoltaic solar module; measuring means for measuring the electrical output from the solar module; first timing means for measuring the length of each interval of time during which the electrical output measured by the measuring means is below a predetermined value; memory means for recording the accumulation of all time intervals measured during the predetermined period of time; and means for displaying the accumulation thus recorded when the accumulation reaches a predetermined value.
A second embodiment of the solar-powered monitor includes a photovoltaic solar module; measuring means for measuring the electric output from the solar module; first timing means for measuring the length of each interval of time during which the electrical output measured by the measuring means is below a predetermined value; second timing means for measuring a predetermined period of time; memory means for recording the accumulation of all time intervals measured during the predetermined period of time; and means for displaying the accumulation thus recorded.